Method and device for adjusting one or more roll segments in a continuous casting installation for casting metals, especially for steel materials

ABSTRACT

A method and a device for adjusting one or more roll segments ( 1 ) in a continuous casting installation for metals, especially for steel materials, the rolls ( 1   a ) of which adjusted in the segment upper frame ( 2 ) and the segment lower frame ( 3 ) on frame cross members ( 5 ) by pairs ( 4 ) of hydraulic piston-cylinder units in a position-and/or pressure-controlled manner, wherein an operation for guiding and/or pressing the casting strands ( 6 ) is switched from a position-controlled to a pressure-controlled operation when pressure within the respective pair ( 4 ) of piston-cylinder units reaches a predetermined maximum value, whereby an improved reaction is effected by operating the piston-cylinder unit of every roll segment ( 1 ) in the case of overload, in subsequent steps at a reduced pressure or in a pressureless switching mode until the switching mode is reached in which the segment upper frame ( 2 ) can be opened to some extent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to method of and to a device for adjusting one ormore roll segments in a continuous casting installation for metals,especially for steel materials, the rolls of which are adjusted in thesegment upper frame and the segment lower frame on frame cross membersby pairs of hydraulic piston-cylinder units in a position-and/orpressure-controlled manner, wherein an operation for guiding and/orpressing the casting strands is switched from a position-controlled to apressure-controlled operation when the pressure within the respectivepair of piston-cylinder units reaches a predetermined maximum value.

2. Description of the Prior Art

In a method for guiding a cast strand with an associated strand guide,the opening width, which corresponds to the thickness of the caststrand, is continuously adjusted during casting so that with a strandguide segment having four piston-cylinder units, two adjacentservo-piston-cylinder units, which are hydraulically combined with eachother, are adjusted in accordance with the strand, and the remainingservo-piston-cylinder units are adjusted independently (DE 196 27336C1).

Proceeding from this known method, WO 99/46 071 discloses the methoddescribed at the beginning. However, the known method and strand guidesdo not encompass all operational processes. In the roll casing, theexisting forces are transmitted from the strand guide roll by a rolleror slide bearing to a respective frame cross-member. During anoperation, which often lasts several days or weeks without aninterruption, stresses of different type and magnitude occur. Therefore,operational conditions most often occur which are caused by particularlyhigh loads. Such operational conditions occur during casting attransition from a cold strand head to a hot strand, are caused, duringcomposite casting, by a connection element between the melts ofdifferent steel products, and occur when the casting ends, i.e., arecaused by strand ends. The strand shape of the transition piece and aski shape generate particularly high loads. The resulting geometry of acast strand is transported through the entire casting installation andpasses every roll segment which results in different local loadconditions. Simultaneously, a continuous strand displacement andsuppression of the strand bulging in insured by the ferrostaticpressure. These conditions require particular measures.

The object of the invention is to compensate an overload that occurredpreviously, by an effective reaction of respective roll segments, i.e.,to provide far-reaching protective measures.

SUMMARY OF THE INVENTION

The object of the invention is achieved by operating, in the case ofoverload, the piston-cylinder units of every roll segment in subsequentsteps at a reduced pressure or in a pressureless switching mode untilthe switching mode is reached in which the segment upper frame can beopened to some extent. Thereby, an effective reaction of the rollsegments at an increasing load is achieved in response to local loadforces, i.e., a controlled reduction of the incoming overload takesplace. The segment upper frames with rolls and bearings actively reduce,at the switching “open”, the build-up overload.

This regulation possibility is expanded due to the fact that in thepressureless switching condition, the weight of the segment upper frameand friction forces of the relative displacement of the cylinder and thepiston of a piston-cylinder unit provide for a locking force.

In order, however, to insure that the “softeners” of the adjusting forcewould not remain unmeasured, it is proposed to retain a maximum gapbetween the roll segments and the cast strand at a limited opening ofthe segment upper frame in the switching mode. Thereby, the setwithdrawal or run-in path includes, for all cases, only a small portionof the entire available run-in path. In case this small run-in path isnot retained, the strand would bulge in an unpermissible high region atan affected point, and the casting process would not be able tocontinue.

A device for adjusting one or more roll segment in a continuous castinginstallation for metals, especially for steel materials, proceeds from adevice the rolls of which are adjusted in the segment upper frame andthe segment lower frame on frame cross member by pairs of hydraulicpiston-cylinder units in a position-and/or pressure-controlled manner,wherein an operation for guiding and/or pressing the casting strands isswitched form a position-controlled to a pressure-controlled operationwhen the pressure within the respective pair of piston-cylinder unitsreaches a predetermined maximum value. The object of the invention withrespect to the device is achieved by providing an adjustabledisplacement stop in the path of the segment upper frame. Thereby, thesegment upper frame is not displaced over the entire possible run-inpath.

In order to avoid a need in additional necessary constructional space,it is proposed to arrange the displacement stop between the segmentupper frame and the segment lower frame.

According to further features, the displacement stop is advantageouslyarranged in immediate vicinity of every piston-cylinder unit. With fourpiston-cylinder units, each piston-cylinder unit includes such adisplacement stop.

A displacement stop consisting of a pivoted-in and a pivoted-out togglelever a pivot axis of which with a first lever arm is supported on thesegment lower frame and its second lever arm lies below the segmentupper frame in a pivoted-in position, proved itself in practice. Thedisplacement stops are only pivoted in for a casting operation. Duringmaintenance shifts, the displacement stop can be pivoted out, whereby acomplete opening and a complete displacement of the segment upper framecan be effected for effecting a maintenance work.

According to other features, the displacement limitation is defined byan abutment mounted on the segment upper frame and forming apredetermined gap.

The gap can be formed by stacking on the abutment of the segment upperframe a plurality of shims for forming a changeable step-by-step gap.For each segment upper frame or for each piston-cylinder unit, thenumber and thickness of the shims is individually selected. Thereby, itis possible to provide an individual adjustment of a basic set-up of adisplacement limitation for each roll segment or for eachpiston-cylinder unit at the entry side of the cast strand and at theexit side of the cast strand.

A further improvement according to the invention consists in forming thedisplacement stop simultaneously as an overload protection element, withthe toggle lever being provided with a predetermined breaking point. Inthis way, the roll segment can be additionally protected from extremeoverloads (so-called special casting cases).

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show an embodiment of the invention which would beexplained in detail further below.

The drawings show:

FIG. 1A a side view of a roll segment in a locking position,

FIG. 1B a detail “A” according to FIG. 1A at an increased scale with thedisplacement stop in the locking position,

FIG. 1C the same detail “A” with the displacement stop outside of thelocking position for maintenance work,

FIG. 2A a front view of a roll segment in the locking position, with thedisplacement stop shown in side view,

FIG. 2B a front view of a roll segment at maximum opening,

FIG. 3 side view of a roll segment without the displacement stop,

FIG. 4A a front view of a roll segment in a locking position without thedisplacement stop,

FIG. 4B a front view of a roll segment outside of the locking positionin a completely open position,

FIG. 5 a side view of a roll segment with a point of application of thedisplacement stop,

FIG. 6A a detail of the support of a toggle lever, and

FIG. 6B a side view of the support of the toggle lever according to FIG.6A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A device according to the present invention, which is shown in FIG. 1,is used in a continuous casting installation for casting metals, inparticular steel materials, and serves for adjusting one or more rollsegments 1, with each roll segment 1 having, e.g., six rolls 1 a (rollpairs) which are rotationally and partially drivingly supported in asegment upper frame 2 and a segment lower frame 3. The segment upperframe 2 and the segment lower frame 3 are adjusted in a sequentialposition-and/or pressure-controlled manner by pairs 4 of piston-cylinderunits supported on a frame cross-members 5, with the sequence beingdetermined by a casting direction 6 a of a cast strand (6) (a slab stripbeing shown). At that, the operation is switched fromposition-controlled to pressure-controlled as soon a pressure within arespective pair 4 of piston-cylinder units reaches a predeterminedmaximum value.

The cast strand 6 can be a slab strand or a bloom cross-section, e.g., adog-bone profile. An adjustable displacement stop 7 (FIGS. 1B and 1C) isprovided in a adjustment path of the segment upper frame. The adjustabledisplacement stop is generally arranged between the segment upper frame2 and the segment lower frame 3. In unit “A”, which is shown in FIG. 1Bat an increased scale, the adjustable displacement stop 7 is formed as atoggle lever 7 a. The toggle lever 7 a is located immediately adjacentto a respective piston-cylinder unit (FIGS. 1A, 2A, 2B and FIGS. 5, 6,and 7). The toggle lever 7 a is secured on the segment lower frame 3with a pivot axle 8. In the embodiment shown in the drawings, the togglelever 7 a has a first lever arm 9 a and a second lever are 9 b. In apivoted-in position 10 (FIG. 1B), an abutment 11, which is secured onthe segment upper frame 2, lies opposite the toggle lever 7 a. Aplurality of shims 13 lie on the abutment 11, so that a maximum gap 12is provided to the pivoted-in displacement stop 7. The gap 12 is notavailable in the locking position according to FIG. 2A and is clearlyvisible in FIG. 2B that shows it maximum size. In the locking position(FIG. 2A), the roller bearing 15, which forms part of a slide or rollingsupport, is subjected to a correspondingly high load.

The displacement stop 7 is simultaneously formed as an overloadprotection element 14. The toggle lever 7 a is provided to that end witha predetermined breaking point 16.

Without the displacement stop 7 (FIG. 3), the casting process would havebeen very inefficient because the withdrawn head of a withdrawn strand,a transition piece between the cold strand and the hot strand, aconnection piece during the composite casting would have beendifferently charged, and a strand piece would have required a “softener”of the locking force, all of which would have required local regulationof the setting force which is possible only to a limited extent.

As can be seen in FIGS. 4A and 4B, without the displacement stop 7, thesegment upper frame 2 with rolls 1 a and the roller bearings 15 wouldhave been pressed against the segment lower frame, and the cast strand 6would have been pressed against its rolls, so that with strands having anon-uniform hardness, different high pressure forces would have beengenerated which only could have been absorbed by opening of the pressurechamber 17 of the hydraulic cylinder 18 by regulating the pressure ofthe hydraulic fluid in a lower pressure chamber 19 with so-called“softeners”.

In case of a maintenance work, a complete opening of the segment upperframe 2 must take place in order to lift the segment upper frame 2 to amost possible extent, as shown in FIG. 4B.

The location of the displacement stop 7 is represented in the embodimentshown in FIG. 5. In FIGS. 6A and 6B, the displacement stop 7 with itstoggle lever 7 a is shown in its pivoted-in position 10 and, with dashlines, in its pivoted-out position (FIG. 6B). The toggle lever 7 a issupported in the segment lower frame 3 by an axle 8, and the abutment 7is provided on the segment upper frame 2, with a plurality of shims 13being stacked on the abutment 7. The shims 13 define a maximum availablegap 12 by which the segment upper frame 2 can be displaced. Thereby, avery short displacement path of the segment upper frame 2 is insured.

List of Reference Numerals

1 Roll Segment

1 a Rolls

2 Segment upper frame

3 Segment lower frame

4 Pairs of piston-cylinder units

5 Frame cross-members

6 Cast strand

6 a Casting direction

7 Adjustable displacement stop

7 a Toggle lever

8 Pivot axle

9 a First lever arm

9 b Second lever arm

10 Pivoted-in position

11 Abutment

12 Gap

13 Shims

14 Overload protection element

15 Roller bearing

16 Predetermined breaking point

17 Pressure chamber

18 Hydraulic cylinder

19 Lower pressure chamber

What is claimed is:
 1. A method of adjusting roll segments (1) in acontinuous casting installation for metal and rolls (1 a) of which aresequentially adjusted in a segment upper frame (2) and a segment lowerframe (3) by pairs of hydraulic piston-cylinder units (4) supported onframe cross-members (5) in position-controlled and pressure-controlledoperations, the method comprising the steps of: switching, in responseto an overload, the piston-cylinder units (4) of each roll segment (1),in following each other steps, from the position-controlled operation tothe pressure-controlled operation for effecting at least one of guidingand pressing a casting strand (6) when pressure within a respective pairof the piston-cylinder units (4) reaches a predetermined maximum value;and displacing the respective pair of the piston-cylinder units (4) in apressureless switching mode until in the switching mode, a predeterminedgap (12) between an abutment (11) provided on the segment upper frame(2) and a lever arm (9 b) of an adjustable displacement stop (7) thatlimits an adjustment path of the segment upper frame (2), is reached ina predetermined pivotal position (10) of the lever arm (9 b), whereby amaximum gap between the roll segments and the strand (6) is provided,with a locking force being provided by weight of the segment upper frameand friction forces of a relative displacement of cylinders and pistonsof the piston-cylinder units.
 2. A device for adjusting roll segments(1) in a continuous casting installation for metal and rolls (1 a) ofwhich are sequentially adjusted in a segment upper frame (2) and asegment lower frame (3) by pairs of hydraulic piston-cylinder units (4)supported on frame cross-members (5) in position-controlled andpressure-controlled operations, wherein in response to an overload, thepiston-cylinder units (4) of each roll segment (1) are switched, infollowing each other steps, from the position-controlled operation tothe pressure-controlled operation for effecting at least one of guidingand pressing a casting strand (6) when pressure within a respective pairof the piston-cylinder units (4) reaches a predetermined maximum value,and the respective pair of piston-cylinder units (4) is displaced in apressureless switching mode, the device comprising: an abutment (11)provided on the segment upper frame (2); and an adjustable displacementstop (7) for limiting an adjustment path of the segment upper frame (2)in the pressureless switching mode, the stop having a lever arm (9 b)that in a predetermined pivotal position (10) of the lever arm (9 b), isspaced from the abutment (11) by a gap (12) providing for a maximum gapbetween the roll segments and the strand (6), whereby a continuouscasting process can take place during the switching mode.
 3. A deviceaccording to claim 2, wherein the displacement stop (7) is arrangedbetween the segment upper frame (2) and the segment lower frame (3). 4.A device according to claim 2, wherein the displacement stop (7) isarranged in an immediate vicinity of every piston-cylinder unit (4). 5.A device according to claim 2, wherein the displacement stop (7) isformed as a pivoted-in and a pivoted-out toggle lever (7 a) a pivot axis(8) of which with a first lever arm (9 a) of the toggle lever (7 a) issupported on the segment lower frame (3), and wherein the gap-forminglever arm (9 b) of the displacement stop (7) forms a second lever armwhich lies below the segment upper frame (2) in the predeterminedpivoted-in position (10).
 6. A device according to claim 2, furthercomprising a plurality of shims (13) stackable on the abutment (11) ofthe segment upper frame (2) for forming a stepwise adjustable gap (12),and a number and thickness of which are selected individually on eachsegment upper frame (2) or on each piston-cylinder unit (4).
 7. A deviceaccording to claim 5, wherein the toggle lever (7 a) simultaneouslyserves as an overload protection element (14) and is provided with abreaking point.